The goal of this study is to use quantitative single-cell RNA-seq to define the molecular signature of RIPK1- mediated inflammatory signaling in glial cells, with a focus on microglia and oligodendrocytes, during aging and investigate the contribution of this pathway to the aging-dependent risk to Alzheimer's disease (AD). AD is the most common age-related neurodegenerative disease that currently affects more than five million Americans ? a number that is expected to nearly triple by 2050. Low-grade, unresolved molecular inflammation may provide an underlying mechanism of aging and age-related diseases, bridging normal aging with age-related pathological processes. Circulating levels of TNF?, a strong proinflammatory cytokine, are elevated in elderly and implicated in the development of AD. Thus, a key question is how chronic neuroinflammation, predominantly mediated by cells of glial lineages, during aging might eventually lead to neuronal cell death and onset of AD. However, the mechanism by which various cell types of the CNS interact to promote the onset of AD is not well understood. The use of single cell RNA-seq may provide an exciting opportunity to explore the mechanism at transcriptomic levels to understand how various glial cells of the CNS, including microglia, astrocytes and oligodendrocytes, interact during aging to mediate inflammation and eventually lead to the development of AD. RIPK1, a key mediator of the innate immune response that regulates both inflammation and cell death, represents an ideal target for reducing cell death and inflammation in the CNS. A RIPK1 inhibitor developed by us has been advanced into a human Phase I clinical trial for the treatment of ALS and AD. Our hypothesis is that the RIPK1-mediated inflammatory process plays an important role in mediating ?microglial priming? for inflammation and in promoting degeneration of oligodendrocytes during aging which set the stage for axonal loss, neural dysfunction and the eventual onset of AD. Specific Aim 1: Investigating the molecular signatures of RIPK1 for age-related changes in the CNS glial lineages at single cell levels using quantitative RNA-seq to explore the mechanisms as to why aging constitutes the biggest risk factor for AD. Specific Aim 2: Identifying aging-related molecular signatures of RIPK1-mediated inflammatory process in microglia of WT and AD mouse models at single cell levels and comparison with human AD. The goal here is to identify key biomarkers for RIPK1-dependent inflammatory processes to be used in the ongoing clinical trial on RIPK1 inhibitor as a new drug for AD. Specific Aim 3: Identifying the molecular signature of RIPK1-mediated age-related changes in astrocytes and oligodendrocytes of WT and AD animal models. Understanding the molecular signature of RIPK1-mediated inflammatory response and cell death and the role of RIPK1 on glial subtypes will provide important biomarkers for guiding the ongoing clinical trial on RIPK1 inhibitor as a treatment for AD.